﻿/*-
 * Copyright 2003-2005 Colin Percival
 * Copyright 2012 Matthew Endsley
 * All rights reserved
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted providing that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
 * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#include <limits.h>
#include "bspatch.h"

static int64_t offtin(uint8_t *buf)
{
    int64_t y;

    y = buf[7] & 0x7F;
    y = y * 256;
    y += buf[6];
    y = y * 256;
    y += buf[5];
    y = y * 256;
    y += buf[4];
    y = y * 256;
    y += buf[3];
    y = y * 256;
    y += buf[2];
    y = y * 256;
    y += buf[1];
    y = y * 256;
    y += buf[0];

    if (buf[7] & 0x80) y = -y;

    return y;
}

int bspatch(const uint8_t *oldFile, int64_t oldsize, uint8_t *newFile, int64_t newsize, struct bspatch_stream *stream)
{
    uint8_t buf[8];
    int64_t oldpos, newpos;
    int64_t ctrl[3];
    int64_t i;

    oldpos = 0;
    newpos = 0;
    while (newpos < newsize)
    {
        /* Read control data */
        for (i = 0; i <= 2; i++)
        {
            if (stream->read(stream, buf, 8))
                return -1;
            ctrl[i] = offtin(buf);
        };

        /* Sanity-check */
        if (ctrl[0] < 0 || ctrl[0] > INT_MAX ||
                ctrl[1] < 0 || ctrl[1] > INT_MAX ||
                newpos + ctrl[0] > newsize)
            return -1;

        /* Read diff string */
        if (stream->read(stream, newFile + newpos, ctrl[0]))
            return -1;

        /* Add old data to diff string */
        for (i = 0; i < ctrl[0]; i++)
            if ((oldpos + i >= 0) && (oldpos + i < oldsize))
                newFile[newpos + i] += oldFile[oldpos + i];

        /* Adjust pointers */
        newpos += ctrl[0];
        oldpos += ctrl[0];

        /* Sanity-check */
        if (newpos + ctrl[1] > newsize)
            return -1;

        /* Read extra string */
        if (stream->read(stream, newFile + newpos, ctrl[1]))
            return -1;

        /* Adjust pointers */
        newpos += ctrl[1];
        oldpos += ctrl[2];
    };

    return 0;
}

#if defined(BSPATCH_EXECUTABLE)

#include <bzlib.h>
#include <stdlib.h>
#include <stdint.h>
#include <stdio.h>
#include <string.h>
#include <err.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <fcntl.h>

static int bz2_read(const struct bspatch_stream *stream, void *buffer, int length)
{
    int n;
    int bz2err;
    BZFILE *bz2;

    bz2 = (BZFILE *)stream->opaque;
    n = BZ2_bzRead(&bz2err, bz2, buffer, length);
    if (n != length)
        return -1;

    return 0;
}

int main(int argc, char *argv[])
{
    FILE *f;
    int fd;
    int bz2err;
    uint8_t header[24];
    uint8_t *old, *new;
    int64_t oldsize, newsize;
    BZFILE *bz2;
    struct bspatch_stream stream;
    struct stat sb;

    if (argc != 4) errx(1, "usage: %s oldfile newfile patchfile\n", argv[0]);

    /* Open patch file */
    if ((f = fopen(argv[3], "r")) == NULL)
        err(1, "fopen(%s)", argv[3]);

    /* Read header */
    if (fread(header, 1, 24, f) != 24)
    {
        if (feof(f))
            errx(1, "Corrupt patch\n");
        err(1, "fread(%s)", argv[3]);
    }

    /* Check for appropriate magic */
    if (memcmp(header, "ENDSLEY/BSDIFF43", 16) != 0)
        errx(1, "Corrupt patch\n");

    /* Read lengths from header */
    newsize = offtin(header + 16);
    if (newsize < 0)
        errx(1, "Corrupt patch\n");

    /* Close patch file and re-open it via libbzip2 at the right places */
    if (((fd = open(argv[1], O_RDONLY, 0)) < 0) ||
            ((oldsize = lseek(fd, 0, SEEK_END)) == -1) ||
            ((old = malloc(oldsize + 1)) == NULL) ||
            (lseek(fd, 0, SEEK_SET) != 0) ||
            (read(fd, old, oldsize) != oldsize) ||
            (fstat(fd, &sb)) ||
            (close(fd) == -1)) err(1, "%s", argv[1]);
    if ((new = malloc(newsize + 1)) == NULL) err(1, NULL);

    if (NULL == (bz2 = BZ2_bzReadOpen(&bz2err, f, 0, 0, NULL, 0)))
        errx(1, "BZ2_bzReadOpen, bz2err=%d", bz2err);

    stream.read = bz2_read;
    stream.opaque = bz2;
    if (bspatch(old, oldsize, new, newsize, &stream))
        errx(1, "bspatch");

    /* Clean up the bzip2 reads */
    BZ2_bzReadClose(&bz2err, bz2);
    fclose(f);

    /* Write the new file */
    if (((fd = open(argv[2], O_CREAT | O_TRUNC | O_WRONLY, sb.st_mode)) < 0) ||
            (write(fd, new, newsize) != newsize) || (close(fd) == -1))
        err(1, "%s", argv[2]);

    free(new);
    free(old);

    return 0;
}

#endif
